We give a fully polynomial-time randomized approximation scheme (FPRAS) for two terminal reliability in directed acyclic graphs (DAGs). In contrast, we also show the complementing problem of approximating two terminal unreliability in DAGs is #BIS-hard.

翻译：本文给出有向无环图(DAGs)中两端可靠性的全多项式时间随机近似方案(FPRAS)。作为对比，我们还证明了DAGs中两端不可靠性近似这一互补问题是#BIS-难问题。